Features

The Various modes guide, when to Intubate, Extubate and confirm Patient Reversal
Also, assists, in identifying, end of Surgical Block OR during Drug top up
Provides Real time, feedback of the strength of contraction ( for TOF, DBS & PTC, modes)

The reason for this is attributed to the binding of non-depolarizing neuromuscular blocking agents to presynaptic acetylcholine receptors, resulting in inhibition of the recruitment of Ach from the reserve pool.

Features

The Various modes guide, when to Intubate, Extubate and confirm Patient Reversal
Also, assists, in identifying, end of Surgical Block OR during Drug top up
Provides Real time, feedback of the strength of contraction ( for TOF, DBS & PTC, modes)

The reason for this is attributed to the binding of non-depolarizing neuromuscular blocking agents to presynaptic acetylcholine receptors, resulting in inhibition of the recruitment of Ach from the reserve pool.

The reason for this is attributed to the binding of non-depolarizing neuromuscular blocking agents to presynaptic acetylcholine receptors, resulting in inhibition of the recruitment of Ach from the reserve pool.

In an attempt to increase the reliability of the TOF-Watch accelerometer a preload device was introduced. According to Claudius, Viby-Mogensen (2008), there is insufficient evidence to confirm or deny that the application of a preload will increase the precision of acceleromyography.

The preload device attempts to restrict the movement of the thumb to one dimension. With a three dimensional accelerometer this is not necessary.

Claudius, C., Viby-Mogensen, J., 2008. âAcceleromyography for Use in Scientific and Clinical Practice â A Systematic Review of the Evidenceâ. Anesthesiology; 108:1117-40

Acceleromyography is based on Newtonâs second law of motion, stating that: F (force) = m (mass) X a (acceleration).

Acceleromyography should be interchangeable with mechanomyography if the mass (in this case the mass of the thumb) is constant.

Surprisingly acceleromyography cannot be used interchangeably with mechanomyography in pharmacodynamic studies.

One difference between mechanomyography and acceleromyography is that the contractions observed during acceleromyography involve a three-dimensional movement involving three joints, frictional forces, and deformation of tissues.

The accelerometer of the TOF-Watch device utilizes a 1-dimensional accelerometer losing much of the information of the complex 3-dimensional movement.

The Stimpod NMS450, on the other hand, uses three accelerometer sensors, each positioned perpendicular on the other two, to enable the device to measure acceleration in three dimensions.

A specialized algorithm processes the information provided by the three accelerometers and provides a value representing the size of the vector of the three dimensional movement.

Xavant is of the opinion that this feature makes acceleromyography more reliable and should bring its response curves more in line with mechanomyography.

No. In order for Stimpod to receive its certification, it has to pass certain tests to prove its immunity to electromagnetic interference (EMI) and electrostatic discharge (ESD). All versions of Stimpod have passed these criteria.

In beginning 2012 the Stimpod was redesigned in order to increase its immunity to EMI and ESD.

The new version of Stimpod has proven its immunity to cauterization in the OR under general conditions, however, extreme intensities of cauterization could still impact of the accuracy and functioning of the Stimpod.

All devices in the OR are generally affected by extreme intensities of cauterization.

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Stimpod NMS410

TheÂ accurate and cost-effective alternative to ultrasound techniques

Increase your accuracy and close needle tip placements

The NMS410âs technology is not only on par with ultrasound techniques when determining anatomical deviations prior to needle insertion, but reduces the duration of the procedure while providing excellent patient comfort and safety.

Features

Simultaneous nerve mapping and nerve location

Auto-sensing technology monitors whether the mapping probe or needle touches the patient and adjusts the current range accordingly.Â With the needle in one hand and the probe in the other, itâs easy to achieve quick and precise nerve location.

Map nerves prior to needle insertion for ultimate accuracy

The nerve mapping probe enablesÂ transcutaneousÂ nerve mapping at higherÂ currents (up to 20mA) to assist in finding deeper peripheral nerves. The small surface area of the tip ensures effective discrimination.

Visual and audible proximity indicator

When the target current and pulse width ranges are reached, the Stimpod will indicate probable nerve proximity. This safety mechanism prevents the practitioner from getting confused with the current settings at different pulse widths while ensuring the needle tip is close to the nerve before administering the block.

Real-time waveform display

The waveform displayÂ indicates if the pulse is delivered according to the settings.Â If the waveform is not square, this indicates excessive impedanceÂ (> 20kOhm) in the circuit which means the ECG electrodes or skin condition needs to be re-assessed before nerve location can be successfully completed.

Simultaneous nerve mapping and nerve location

Auto-sensing technology monitors whether the mapping probe or needle touches the patient and adjusts the current range accordingly. With the needle in one hand and the probe in the other, itâs easy to achieve quick and precise nerve location.
Map nerves prior to needle insertion for ultimate accuracy

The nerve mapping probe enables transcutaneous nerve mapping at higher currents (up to 20mA) to assist in finding deeper peripheral nerves. The small surface area of the tip ensures effective discrimination.
Visual and audible proximity indicator

When the target current and pulse width ranges are reached, the Stimpod will indicate probable nerve proximity. This safety mechanism prevents the practitioner from getting confused with the current settings at different pulse widths while ensuring the needle tip is close to the nerve before administering the block.
Real-time waveform display

The waveform display indicates if the pulse is delivered according to the settings. If the waveform is not square, this indicates excessive impedance (> 20kOhm) in the circuit which means the ECG electrodes or skin condition needs to be re-assessed before nerve location can be successfully completed.

Instructions for use

Technical Service Manual

Support

Frequently Asked Questions

Nerve mapping is a technique whereby superficial peripheral nerves can be traced and located transcutaneously for peripheral nerve blocks during regional anaesthesia procedures. The technique enables the anesthesiologist to determine the site for needle insertion prior to puncturing the skin.

The current density radiates outward from the nerve mapping pen in a spherical form. There is also a decrease in behavioural density as the distance is increased from the source. Axons with a larger diameter exhibit a lower activation threshold than small axons. This results in electrical stimulation activating larger axons first before activating the smaller axons. Looking at the behavioural density, most of the axons will be activated close to the probe, whereas only the larger diameter axons will be activated further away from the probe. There are two options to increase the energy delivered to a nerve without changing the distance from the electrode â increase the current amplitude and/or increase the pulse width.

There is an optimal Pulse Width at which a specific nerve is most excitable. This is called the chronaxie threshold. It is preferable to keep the pulse width as close to this value for the related nerve or nerve plexus, as the Peripheral Nerve Stimulator allows, then increase only the current.

It should be noted that, although there are many published values for chronaxie for various excitable tissues, the range of variability for a given tissue type is quite large. It is generally assumed, however, that nerves can be classified according to their chronaxie thresholds as follows:

Classification

Chronaxie

Sensory Functions

A (alpha)

40-100Îźs

Predominantly motor neurons. They also have
the following sensory functions: Proprioception,
hair receptors, vibratory sensors and high
discrimination touch

A (delta)

150Îźs

Deep pressure and touch, pricking pain and cold

C

400Îźs

Crude touch and pressure, tickle,
aching pain, cold and warmth

From the above table, it would seem reasonable to deduce that the ideal pulse width to facilitate a motor nerve response (A alpha), would be around 100Îźs. If one sets the nerve stimulator at 100Îźs and increases the amplitude to 5mA giving a total charge of 500nC one would not get the same muscle response as if the setting is at 500Îźs and 1mA, also giving a total charge of 500nC. In the second case even though the total charge transferred to the nerve is the same, because of the chronaxie threshold of 100Îźs for the nerve, much of the energy transferred to the nerve after the 100Îźs is wasted on the nerve.

This is clearly shown by the graph below. The strength-duration curve (green) indicates the current necessary at the different pulse widths to facilitate a contraction. The energy cost or total charge is shown by the blue curve. It can be seen that the stimulation is the most energy efficient at the chronaxie pulse of +- 80Îźs width as would be expected. It should be noted how the energy cost increases when pulse width increases.

As a preference, keep the nerve stimulator at a 100Îźs pulse width and adjust the current. If the nerve stimulator is already set at 20mA and the Nerve Mapping Probe does not elicit any neuromuscular response, increasing the pulse width to 300Îźs will offer 3 x more charge, however bear in mind that the net effect on the nerve will not constitute a contraction which is 3 times more powerful.

Due to the fact that the surface location of the nerve is pre-determined and thus the optimal entry point for the needle, the technique reduces the need for multiple needle insertions and discomfort to the patient. It also reduces the time to perform the peripheral regional nerve block.

The nerve mapping technique may be used for various approaches to the brachial plexus, as well as the axillary, musculo-cutaneous, ulnar, median and radial nerve blocks of the upper limb; and the femoral, sciatic and popliteal nerve blocks in the lower limb. Surface nerve mapping is particular useful where classic anatomical landmarks are absent or difficult to define, for example in children with contractures (arthrogryposis multiplex congenital; burns) or with major congenital limb defects.

The Stimpod peripheral nerve stimulator allows the user to use the needle and probe simultaneously, eliminating the need to change cables or make markings on the patient.

The practical application of nerve mapping as a technique has always been a cumbersome technique. In order to use nerve mapping effectively, the position and angle of the probe must be recorded exactly before inserting the needle. Marking the probe position with a marker has proved unsuccessful and cumbersome, as this does not capture the exact position and angle relating to subcutaneous structures â i.e. bone structure, muscles etc. It is important to have the ability to keep the probe in its original position when inserting the needle. This will ensure exact positioning and angle of the needle.

The Stimpod peripheral nerve stimulator facilitates this procedure by providing a combined Nerve Mapping/Locating cable. The unit will automatically switch between the probe and the needle, depending on which device is in contact with the skin. The Stimpod will guide you through the entire procedure, switching between the probe and the needle as needed whilst keeping an eye out for high impedance and nerve proximity.